And they mostly fall into two sizes… stellar and supermassive. The size difference has to do with how much mass they contain versus that of our own sun or solar mass.

For some time now, astronomers have also theorized that black holes with a size between stellar – 100 to a million solar masses – and supermassive – hundreds to billions solar masses, called intermediate-mass black holes, also exist but their existence has never been confirmed.

While astronomers have been observing objects since the 1970s that they thought were intermediate-mass black holes, they weren’t able to measure the objects mass because they defied measurement techniques.

That is until perhaps now when a team of astronomers at the University of Maryland writing in the journal Nature announced that they were able to accurately measure an intermediate black hole which they said confirms the existence of the medium sized hypothetical astral object.

The researchers admitted that while the intermediate-mass black hole they studied may not have been the first to be measured, they say it was the first to be accurately measured.

“Objects in this range are the least expected of all black holes,” University of Maryland astronomy professor Richard Mushotzky said in a press release.

Mushotzky, who is the study’s co-author said; “Astronomers have been asking, do these objects exist or do they not exist? What are their properties? Until now we have not had the data to answer these questions.”

The black hole observed and measured by the University of Maryland team has a solar mass of 400 resides in the Messier 82 galaxy, which is also known as NGC 3034, Cigar Galaxy or M82, located about 12 million light years from Earth in the constellation Ursa Major.

Astronomers working with NASA’s Chandra X-Ray Observatory in 1999 were making observations on the M82 galaxy when they noticed some X-rays coming out of a bright object.

They called the object M82 X-1 and suspected that it might be an intermediate-mass black hole. Astronomers at that time weren’t able figure out its mass, so the object remained unconfirmed.

The astronomers then turned to NASA’s Rossi X-Ray Timing Explorer (RTXTE) a satellite telescope that made about 800 observations of the M82 X-1 object between 2004 and 2010. The RTXTE recorded the x-rays that were produced by M82 X-1.

Dheeraj Pasham, an astronomy graduate student at the University of Maryland and lead author of the study, took the data that was gathered by the RTXTE and was able to map both the intensity and wavelength of those x-rays in each of the observational sequences. Pasham then linked all the sequences together and then made an analysis of the compiled data.

Artist impression of Rossi X-Ray Timing Explorer (RXTE) in orbit. Data recorded by this satellite was used to measure intermediate-mass black hole (NASA)

Pasham noticed something odd from among the material that was circling the supposed black hole. He noticed two repeating flares of light that were pulsating at a consistent rhythm. One of the two light flares pulsed about 5.1 times per second while the other 3.3 times per second. Together the two light flares were pulsing at a ratio of 3:2.

This pulsing 3:2 rhythm of light has provided astronomers with a technique to measure a black hole’s mass.

But it had been used to measure smaller black holes, not on objects suspected of being intermediate-mass black holes.

Nonetheless, Pasham and his colleagues went ahead and applied the 3:2 oscillation technique to determine the mass of the object. His calculations showed that the M82 X1 has an estimated mass of about 428 times the mass of the sun, plus or minus about 105 solar masses.

Rick Pantaleo maintains the Science World blog and writes stories for VOA’s web and radio on a variety of science, technology and health topics. He also occasionally appears on various VOA programs to talk about the latest scientific news. Rick joined VOA in 1992 after a 20 year career in commercial broadcasting.